router: consistently format IP addresses when printing
router: consistently format IP addresses when printing

We need to escape IPv6 addresses in brackets, so added a small helper to
do that when necessary.  This should make the output more consistent.

grobian/carbon-c-relay,piotr1212/carbon-c-relay,grobian/carbon-c-relay,piotr1212/carbon-c-relay,piotr1212/carbon-c-relay,piotr1212/carbon-c-relay,grobian/carbon-c-relay